This invention relates generally to an electronic note generator used to output melodies and the like and more particularly to an electronic note generator having a volume control free of variable resistors. In the prior art there are several methods to control the volume of sound output. For example, the division ratio of a variable resistor is used to control volume, the gain of an amplifier is varied, or logic techniques are used to form sound waves with controlled amplitude.
When using a resistor which is tapped to provide different ratios of resistance, it is difficult to include such a volume control system within an integrated circuit because of the difficulty in providing a resistance with accurate value due to variations in the manufacturing process. When using an amplifier of variable gain for volume control, the amplifier is generally used in an analog circuit. Controlling the amplifier for volume control in a digital circuit is complicated both with regard to the accuracy and construction of the amplifier. Further, there is a problem with the linearity of the amplifier. In a logic control circuit for amplitude control, such techniques as digital to analog transformation require a complicated circuit construction in the digital circuit as shown by the method of synthesizing the sound.
What is needed is a volume control for an electronic note generator which does not require adjustment in division ratio of a resistor, rely on a variable gain amplifier or use complex logical circuit techniques.